i think you have a blockbuster there.
charlize theron wasn't creepy enough. swinton could do it in a much more convincing way. she would have to kill them very, very slowly--over several days.
maybe with paper cuts.
or, maybe she could suck their blood out, but only an ounce or so each day.
kind of like a psychotic lesbian version of "attack of the giant leeches".
i'm sure it would be BIG!